The main function of DNS (“Domain Name System”) is to accurately locate network resources on the basis of the corresponding relationships between domain names and IP addresses, namely to search IP addresses according to their domain names.
FIG. 1 is a flow chart which schematically shows a typical tree structure of domain space. At the most upper of the chart, the only root of the DNS tree structure is denoted by dot “.”. The next level of the root is called as Top Level Domain (e.g., “com”), the next level of the Top Level Domain is Second Level Domain (e.g., “shtele.com”), the next level of the Second Level Domain is Third Level Domain (e.g., “John.shtele.com”), and the rest may be inferred. Each domain is a sub-domain of its superior domain, and has a DNS server to store domain name information in the form of resource records. Ordinary types of resource records include: (1) A address record, which lists the corresponding relationship between the IP address of the specific host's name and its domain name, which is an important record for domain name resolution; (2) AAAA address record, which translates DNS domain name into 128-bit IPv6 address; (3) Domain Name Server record, which assigns the relationship between the IP address of the domain name server dominating a given region and its domain name; and other types of resource records. When utilizing DNS service, users need not understand the typical tree-structural hierarchy for domain space of DNS in detail. And they only need to designate one DNS server or use Dynamic Host Configuration Protocol (“DHCP”) and other relevant technology when configuring network. Users' application programs can access DNS system through the resolver embedded in the operating system to search the information of network resources in relation to domain names.
The deployment of IPv6 eases the pressure resulting from the limitation of addresses existing in IPv4, while it is much more difficult to memorize a 128-bit IPv6 address as compared with a IPv4 address. Therefore, the domain names are used more widely in IPv6 network. In IPv6 network, each device will be registered with a globally unique domain name by the domain name configuration system. For instance, in IPv6 home network, each home device will possess an IPv6 address in the near future, and users are able to remotely access their home network devices by means of the domain name configuration.
Currently, there are two methods for domain name configuration in IPv6: (1) manually adding resource records (the translating relationships between addresses and domain names) to the DNS server of the present level; (2) At present automatic configuration RA (“Router Advertisement”) option, DHCPv6 option and DDNS (“Dynamic Domain Name Server”) option. RA option: it defines RDNSS, a new Neighbor Discovery (ND) option containing the DNS server's address and being able to utilize current ND request and advertisement options, which is illustrated in FIG. 2A; DHCPv6 option: illustrated in FIG. 2B, in the condition of stateful DNS server discovery, DHCPv6 employs FQDN (Fully Qualified Domain Name) option of DHCP to enable the terminal device to automatically register a domain name on the DNS server when configuring the DHCPv6 service; DDNS option: illustrated in FIG. 2C, DDNS Option installs DDNS client software on the user's host and thus enables it to automatically register one domain name on a remote DDNS server after each address configuration. In this way, other hosts can access the user's host via DDNS server even if the user's host has no fixed IP address.
The aforesaid automatic configuration methods are only applicable to a simple user network within a local area, such as enterprise network, campus network or home network. As to large-area access network, there would be lots of limitations if the above domain name configuration methods were employed: (1) the negotiations of registration requests from enormous users' hosts on the network SP's (“Service Provider”) DNS server are not secure and difficult to be managed. (2) The biggest defect of DDNS is that each device need to be installed with DDNS client software, and logging on and authentication must be also conducted, which is not suitable for the circumstance such as IPv6 home network which has many home devices. Moreover, in DDNS, the users could not clearly know about the domain name status of their own home devices and conduct unified management such as modification and deletion, etc.
Therefore, for users within large area, a mechanism of hierarchical management should be established to easily manage domain names. At the same time, it is necessary to conduct hierarchical configuration of domain name between the DNS server in local scale and the network SP's DNS server so as to realize the remote access to devices in local scale, such as the terminal devices in the home network.